I've been playing around with Emby Media Server lately and decided to see if I could improve the DLNA config to better support the N900. Having tweaked one of the built-in profile *.xml files I came up with the following. It seems to work OK in both Media Player and OMP for me but I expect there to be some improvements that can be made. I can't get album art or seeking to work for example. Large libraries will take some time to appear/navigate.

It uses the N900's user-agent, GUPnP/0.13.2, as a way of identifying itself. If you have any other renderers with the same basic ID it may cause an issue. If anyone has a better way please feel free to post it.

Windows users: Place in C:\Users\YourUserName\AppData\Roaming\Emby-Server\config\dlna\user as "Nokia N900.xml"
Linux: can't remember off the top of my head.